Note 12 - Equity Incentive Plan - Stock Options and SAR's Activity (Details)	12 Months Ended
	Dec. 31, 2017 $ / shares	Dec. 31, 2016 $ / shares
Options and SAR's outstanding at beginning of year	979,569	762,260
Options and SAR's outstanding at beginning of year, Weighted Average Exercise Price Per Share (in dollars per share)	$ 26.15	$ 18.75
Options and SAR's Granted	440,688	354,275
Options and SAR's Granted, Weighted Average Exercise Price Per Share (in dollars per share)	$ 50.22	$ 40.77
Options and SAR's Cancelled	(74,527)	(58,841)
Options and SAR's Cancelled, Weighted Average Exercise Price Per Share (in dollars per share)	$ 45.56	$ 30.05
Options and SAR's Expired	(589)	(3,310)
Options and SAR's Expired, Weighted Average Exercise Price Per Share (in dollars per share)	$ 32.86	$ 11.37
Options and SAR's Exercised	(17,941)	(74,815)
Options and SAR's Exercised, Weighted Average Exercise Price Per Share (in dollars per share)	$ 20.56	$ 15.46
Options and SAR's outstanding at end of year	1,327,200	979,569
Options and SAR's outstanding at end of year, Weighted Average Exercise Price Per Share (in dollars per share)	$ 33.70	$ 26.15